Yes! It’s set in the same world as FDSTS (after the Earth was devastated by the Reduction and the wars of the Reduction), and in the same time period as FDSTS (a few generations after healthy children start being born to the Reduced). However… Star-Swept takes place in a different land called New Pacifica, where society responded very differently than the Luddites of FDSTS to the Reduction and the wars. (And you find out int eh book how and why, and why their history was thus remarkably different.) As you may have guessed from the description, they aren’t anti-technology at all.

Are Kai and Elliot in this book?

Spoilers! But I will say that you will recognize some of the characters in Star-Swept. If you’re familiar with Kristin Cashore’s books Graceling and Fire, it’s kind of like that. This book is set in a different society, with different main characters, but you will meet some familiar faces along the way.